Childhood aggressivity at age 7 is associated with a fourfold increased risk for illicit drug dependence at age 25. Despite high rates of aggressivity in children with histories of parental neglect, theory-driven and efficacious drug prevention programs to curtail key precursors of youth substance use initiation (SUI) have not been adapted nor experimentally evaluated with neglected children placed in regular foster homes. The proposed project addresses this critical gap by initially testing a multi-component (child, parenting, and co parenting) early drug prevention intervention for children, their biological parent, and foster parent. The psychosocial intervention is based on a transtheoretical approach (psychobiology of neglect, social learning theory, and family systems) to show improvement primarily in early predisposing SUI processes, child aggressivity, and positive parenting, and secondarily in neuroendocrine (cortisol) functioning, supportive co parenting, and foster home stability by: (1) child training;(2) parenting training;and (3) co parenting training. The intervention is delivered via 12-week Parent and Child Groups which utilizes the Incredible Years programs adapted for a foster care population and led by trained hybrid university-foster agency worker teams. Parenting and Co parenting components are integrated in a joint (multiple biological and foster pairs) parent group format. Groups take place in the foster agency where the children are served. Five foster care agencies and NYU Child Study Center have joined in a community-academic partnership to implement the pilot intervention with N = 100 families. The study uses a within agency design to assign families to intervention (N= 50) or a 'usual care'comparison (N = 50) conditions. A plan to reduce contamination risk is in place. Due to their maltreatment histories, all participating children are considered high-risk for child aggressivity. Three assessments will be conducted: pre-intervention (wave1), postintervention (wave2), and 6 month follow-up after intervention (wave3). Data are gathered from the biological parent, foster parent, child, teacher, a trained observer, and CPS records regardless of whether the child remains in foster care, is discharged home, or enters a preadoptive home. We will complete power analyses regarding the magnitude of intervention effects in primary and secondary outcomes in preparation for a large-scale clinical trial;and feasibility studies (attendance and fidelity) involving this multi component intervention. This application has considerable public health relevance because it will provide information of the value of training frontline foster agency workers in evidence-based interventions, and potentially serve as a model for promoting efficacious protection to SUI for underserved high risk children and their families.